Mass-flow sensor with a molded flow restrictor

Abstract

A high mass-flow sensing apparatus and method of forming the same, comprising a flow tube bypassed in a flow path defined by a flow channel, through which a fluid flows. A flow sensor can be disposed in the flow tube for measuring a flow rate of the fluid in the flow channel. A set of narrow rectangular flow restrictors can be molded into the flow tube and adjacent to the flow sensor. Each flow restrictor can include several rectangular cutouts that are molded into upstream and / or downstream portions of the flow tube in order to limit the flow rate of the fluid across the flow sensor. The flow restrictors can laminarize the flow rate of the fluid in the flow tube and thereby reduce flow turbulence and lead to optimal sensing performance of the flow sensor.

Description

TECHNICAL FIELD[0001]Embodiments are generally related to mass-flow sensing devices and methods. Embodiments are also related to airflow sensors that incorporate the use of a molded flow restrictor. Embodiments are additionally related to an improved method for providing flow restriction utilizing a flow restrictor.BACKGROUND OF THE INVENTION[0002]Fluid flow rate control mechanisms are utilized in a variety of flow systems in order to control the amount of fluid such as, for example, gas or liquid, passing through a flow system. Flow control mechanisms can be utilized to regulate flow rates in systems such as ventilators and respirators for maintaining a sufficient flow of breathable air or providing sufficient anesthetizing gas to a patient in preparation for surgery. Typically, flow rate control occurs through the utilization of control circuitry responsive to measurements obtained from fluid flow sensors. Such a fluid flow sensor may be configured to measure properties of a fluid...

AI Technical Summary

Benefits of technology

[0009]The aforementioned aspects and other objectives and advantages can now be achieved as described herein. A mass-flow sensing device and a method of forming the same are disclosed. The mass-flow sensing device / apparatus generally includes a flow tube bypassed in a flow path defined by a flow channel, through which a fluid flows. The flow tube is preferably formed from a plastic material, but may be formed from another material. A flow sensor (e.g., an airflow sensor) can be disposed in the plastic flow tube for measuring a flow rate of the fluid in the flow channel. A set of narrow rectangular flow restrictors can be molded into the plastic flow tube and positioned adjacent to the airflow sensor. The rectangular flow restrictors have a laminarizing effect on the flow of the fluid in the flow tube, thereby reducing flow turbulence, which can lead to an optimal sensing performance of the airflow sensor.

[0010]Furthermore, the rectangular cutouts of the flow restrictors can form a number of orifices adapted to the flow tube for producing a uniform flow of fluid across the flow tube. The flow restrictors can promote a bi-directional flow of the fluid through the flow tube. Such flow restrictors can provide enhanced laminarization of the fluid flow as well as an improved calibration between the airflow sensor and the flow restrictor, thereby producing more accurate flow measurements. The high-mass-flow sensing device disclosed herein can therefore avoid flow turbulence and output saturation at a low cost without the need for additional pressure restriction in the flow path of the bypass flow channel.

Problems solved by technology

Such flow sensors are susceptible to mis-measurement due to turbulent flow effects (e.g., non-uniformity in flow velocity and pressure), and thus the accuracy of such sensors may be adversely affected by such factors.

Such sintered restrictors and orifices are costly to manufacture.

Orifices produce a flow jet, which can lead to an increase in flow turbulence.

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